Parameterize the import directories, fix test to behave correctly on an error

pkg/intl/lib/generate_localized.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * This provides utilities for generating localized versions of
  * messages. It does not stand alone, but expects to be given
  * TranslatedMessage objects and generate code for a particular locale
  * based on them.
  *
  * An example of usage can be found
  * in test/message_extract/generate_from_json.dart
  */
 library generate_localized;
 
 import 'extract_messages.dart';
 import 'src/intl_message.dart';
 import 'dart:io';
 import 'package:pathos/path.dart' as path;
 
 /**
+ * If the import path following package: is something else, modify the
+ * [intlImportPath] variable to change the import directives in the generated
+ * code.
+ */
+var intlImportPath = 'intl';
+
+/**
+ * If the path to the generated files is something other than the current
+ * directory, update the [generatedImportPath] variable to change the import
+ * directives in the generated code.
+ */
+var generatedImportPath = '';
+
+/**
+ * Given a base file, return the file prefixed with the path to import it.
+ * By default, that is in the current directory, but if [generatedImportPath]
+ * has been set, then use that as a prefix.
+ */
+String importForGeneratedFile(String file) =>
+    generatedImportPath.isEmpty ? file : "$generatedImportPath/$file";
+
+/**
  * A list of all the locales for which we have translations. Code that does
  * the reading of translations should add to this.
  */
 List<String> allLocales = [];
 
 /**
  * This represents a message and its translation. We assume that the translation
  * has some identifier that allows us to figure out the original message it
  * corresponds to, and that it may want to transform the translated text in
  * some way, e.g. to turn whatever format the translation uses for variables
@@ skipping 57 matching lines @@
  */
 String prologue(String locale) => """
 /**
  * DO NOT EDIT. This is code generated via pkg/intl/generate_localized.dart
  * This is a library that provides messages for a $locale locale. All the
  * messages from the main program should be duplicated here with the same
  * function name.
  */
 
 library messages_${locale.replaceAll('-','_')};
-import 'package:intl/intl.dart';
-import 'package:intl/message_lookup_by_library.dart';
+import 'package:$intlImportPath/intl.dart';
+import 'package:$intlImportPath/message_lookup_by_library.dart';
 
 final messages = new MessageLookup();
 
 class MessageLookup extends MessageLookupByLibrary {
 
   get localeName => '$locale';
 """;
 
 /**
  * This section generates the messages_all.dart file based on the list of
  * [allLocales].
  */
 String generateMainImportFile() {
   var output = new StringBuffer();
   output.write(mainPrologue);
   for (var each in allLocales) {
-    output.write("import 'messages_$each.dart' as ${asLibraryName(each)};\n");
+    var baseFile = 'messages_$each.dart';
+    var file = importForGeneratedFile(baseFile);
+    output.write("import '$file' as ${asLibraryName(each)};\n");
   }
   output.write(
     "\nMessageLookupByLibrary _findExact(localeName) {\n"
     "  switch (localeName) {\n");
   for (var each in allLocales) {
     output.write(
         "    case '$each' : return ${asLibraryName(each)}.messages;\n");
   }
   output.write(closing);
   return output.toString();
 }
 
 /**
  * Constant string used in [generateMainImportFile] for the beginning of the
  * file.
  */
-const mainPrologue = """
+var mainPrologue = """
 /**
  * DO NOT EDIT. This is code generated via pkg/intl/generate_localized.dart
  * This is a library that looks up messages for specific locales by
  * delegating to the appropriate library.
  */
 
 library messages_all;
 
 import 'dart:async';
-import 'package:intl/message_lookup_by_library.dart';
-import 'package:intl/src/intl_helpers.dart';
-import 'package:intl/intl.dart';
+import 'package:$intlImportPath/message_lookup_by_library.dart';
+import 'package:$intlImportPath/src/intl_helpers.dart';
+import 'package:$intlImportPath/intl.dart';
 
 """;
 
 /**
  * Constant string used in [generateMainImportfile] as the end of the file.
  */
 const closing = """
     default: return null;
   }
 }
 
 /** User programs should call this before using [localeName] for messages.*/
 initializeMessages(localeName) {
   initializeInternalMessageLookup(() => new CompositeMessageLookup());
   messageLookup.addLocale(localeName, _findGeneratedMessagesFor);
   return new Future.immediate(null);
 }
 
 MessageLookupByLibrary _findGeneratedMessagesFor(locale) {
   var actualLocale = Intl.verifiedLocale(locale, (x) => _findExact(x) != null);
   if (actualLocale == null) return null;
   return _findExact(actualLocale);
 }
 """;